A gas turbine engine includes a combustor which generates hot combustion gases which flow downstream therefrom and through a turbine nozzle which suitably directs the flow into a row of turbine blades which extract energy therefrom. The turbine nozzle includes a plurality of circumferentially spaced apart stator vanes mounted radially between radially inner and outer bands which confine the combustion gas flow. Disposed radially outwardly of the turbine blades are a plurality of circumferentially adjacent shrouds which also confine the combustion gas flow.
Both the nozzle bands and the turbine shrouds are typically cooled by channeling thereto cooling air which is bled from the compressor of the engine.
Turbine shrouds typically have forward and aft hooks extending radially outwardly therefrom for conventionally mounting the shrouds to stationary components of the engine. In one exemplary design, the leading edge of the shroud extends axially upstream from the leading edge of the turbine blades and effects a relatively large overhang as measured between the shroud leading edge and the forward hook from which it is supported. The turbine shrouds are typically cooled by providing bleed air from the compressor into the shroud between the forward and aft hooks thereof through a suitable impingement baffle which directs the cooling air in impingement against the radially outer surface of the shroud. The shroud typically includes a plurality of rows of inclined film cooling holes which extend through the shrouds, with inlets disposed between forward and aft hooks and outlets at the leading edge overhang. As the overhang lengths increases, the lengths of the film cooling holes also increases which decreases the effectiveness of cooling the overhang since the cooling air increase in temperature at it travels through the relatively long, thin cooling holes. Improved cooling configurations are desired for turbine shrouds having particularly large overhangs.